The paper quotes “people familiar with the probes” who say antitrust enforcers are concerned that the three companies hid patents in order to be ahead of the competition when industry-wide interchangeability standards are set.

The investigation will focus on whether, while involved in drafting the standards, the firms did not disclose patents or patent applications that would later mean other companies had to pay them royalties, the report said.

Sun, Rambus and Unocal have all filed patent infringement suits against firms they say owe them royalties, said USA Today.

However, those companies then countersued, charging the three with concealing their patents, and complained to the FTC, said the report.

The Sun investigation covers Sun’s alleged failure to disclose patents when helping to draft an industry standard for computer memory modules, and subsequent request for royalties from competitors, said the report.

The Unocal case covers its patents on clean-fuel formulations, which it completed while helping to draft gasoline standards. Those standards now virtually mandate the use of Unocal’s process, USA Today said.

Rambus is said to have pushed the computer industry to adopt a memory-chip standard while seeking patent rights to it.

The FTC has confirmed that it is investigating Unocal but would not confirm that investigations were underway into Sun and Rambus, the paper said.